This invention constitutes an improvement over the lenticular seal disclosed and claimed in U.S. Pat. No. 3,733,146 granted to S. L. Smith & P. E. Voyer on May 15, 1973 and assigned to the same assignee as this patent application. This patent discloses a toroidally shaped seal disposed between the 1st and 2nd turbine and is lenticular in cross section. Essentially, the inner and outer curved plates form an elliptical body that has its narrow ends abut against the adjacent disks of the turbines or the side plates thereof. This, in fact, forms a point attachment in cross section, and a circumferential edge attachment in full, being supported radially by the turbine disks and transmitting the axial load through both curved plates. In operation, the plates achieved their results, that is, net reduced stress, by virtue of the bending of the plates. Obviously, the higher the bending loads the heavier the plates have to be so as to tolerate the higher bending stresses. Other patents that disclose seals or spacers between turbine disks are U.S. Pat. Nos. 3,094,309, 3,894,324 and 4,127,359.
I have found that I can achieve the sealing capabilities of the lenticular seal yet provide a lighter weight structure that affords additional features not heretofore attainable with the lenticular seal. According to this invention, the seal on the outer diameter has a rim element that has a virtually flat annular surface and on the inner diameter has a rim element that has a convexed annular surface and both rims are attached by a vertical disk much like an "I" beam in cross section. The outer rim is concentric to the centerline and transmits the axial loads. Because of this configuration the outer rim provides a stiffer backbone to the axial stresses exerted by the turbine disks and serves to tune the vibrations of the 2nd turbine. The inner rim abuts against a projection extending axially from the adjacent turbine disks and may be slightly conical in shape convexing toward the centerline. This member transmits the radial load and it, itself, takes some of the radial load by transmitting some of the load to the outer rim through the transverse member, thus minimizing the radial stress placed on the turbine disks. Lugs on the inner rim cooperate with lugs on the turbine disks to prevent rotation of the seal in the event of slippage. The lugs of the inner rim cooperate with the disk of the second stage turbine to assure that the pressure drop across the transverse member doesn't exceed a predetermined value. Further, the seal may include a vertical projection member (hammer head) adjacent the rear side plate of the first turbine to exert a load upon rotation to retain it in place.